Don't worried sir I'm in Puerto Rico so if I have a new orders of Dx Super A PCB it will be post here.
Regards
Juan
As you see dear Juan, by forgiven question... we must provide
to them these pcboards....the supply pcboard and the Dx Super A pcboard.
I do suggest you to ask interested people to post their interest to have these pcboards, inform price and them proceed the order.
If we do not do that...you see that people may run to pirates.
These guys are not authorized..they just copy our forum files and produce pcboards to sell...they are bandit.
If we do not offer boards, then we cannot ask people not to buy from them.
I would like them not to get involved with piracy, but we have to give them support, we have to offer good conditions for them "not to need to buy from pirates"
Reduce your pcboard features to reduce price...as Ebay is offering is not good things and because not that good their price is low....so.... try to compete...but do not make it entirelly for free...yours pcboards must be for free for you...so...your unit must be included in the cost price.
regards,
Carlos
to them these pcboards....the supply pcboard and the Dx Super A pcboard.
I do suggest you to ask interested people to post their interest to have these pcboards, inform price and them proceed the order.
If we do not do that...you see that people may run to pirates.
These guys are not authorized..they just copy our forum files and produce pcboards to sell...they are bandit.
If we do not offer boards, then we cannot ask people not to buy from them.
I would like them not to get involved with piracy, but we have to give them support, we have to offer good conditions for them "not to need to buy from pirates"
Reduce your pcboard features to reduce price...as Ebay is offering is not good things and because not that good their price is low....so.... try to compete...but do not make it entirelly for free...yours pcboards must be for free for you...so...your unit must be included in the cost price.
regards,
Carlos
So far - So good.....
Hi friends!
Sorry for the silence, but today I got the last components soldered in and the power supply board is finished too. Please enjoy the photos and add comments.
About the power supply: 30V/100VA transformer, 25A bridge plus a CRC filter, 10000uF (3x3300), 0,5 Ohm/5W and again 10000uF.
Next will be testing of the amp boards. I plan to use a 30V lab supply for the adjustments of idle conditions. Then I need to test and connect the real supply and adjust one more time. And after that load testing.....
Hi friends!
Sorry for the silence, but today I got the last components soldered in and the power supply board is finished too. Please enjoy the photos and add comments.
About the power supply: 30V/100VA transformer, 25A bridge plus a CRC filter, 10000uF (3x3300), 0,5 Ohm/5W and again 10000uF.
Next will be testing of the amp boards. I plan to use a 30V lab supply for the adjustments of idle conditions. Then I need to test and connect the real supply and adjust one more time. And after that load testing.....
Attachments
Nice... But no insulation and silicon compound all tranies on the heatsink?
Good eyes! Wow, I did not notice that those transistors do not have the insulations or compound.
@ Carlos: Thank you very much for the schematics and support! We will need more of that when the thing starts to make music....
@wiljj78, lanchils and project16: I already DID power it up....
But without heat sinks of course, hahaha
Forgetting the insulation pads is a classic error, thank you for the warning!
Both modules idle perfectly at a around 25 ma as in the instruction and the voltage is adjusted to half of the supply.
The power supply works, but seems to blow the 4amp fuses when I switch it on. I must be because of the inrush current into the 20mF capacitance! A 22ohm/9mm thermistor at the transformer primary seems to solve the problem, but some more experimentation will be needed.
Stay tuned....
nnx
@wiljj78, lanchils and project16: I already DID power it up....
But without heat sinks of course, hahaha
Forgetting the insulation pads is a classic error, thank you for the warning!
Both modules idle perfectly at a around 25 ma as in the instruction and the voltage is adjusted to half of the supply.
The power supply works, but seems to blow the 4amp fuses when I switch it on. I must be because of the inrush current into the 20mF capacitance! A 22ohm/9mm thermistor at the transformer primary seems to solve the problem, but some more experimentation will be needed.
Stay tuned....
nnx
Good to know it is working, But it is a bad idea to power an amplifier without heatsinks too
the heatsink is a common ground for the amp to establish operating bias as the amp heats up, with out it thermal run-away will happen....
Hmmmm, I understand.
But with a current limited lab supply everything went fine. The outputs got a little warm as the idle current climbed up to 40ma , but a touch with the fingertip on the vbe transistor made it come back down to 25ma. That indicates thea the bias servo works as intended.
Fuses are fast blow, need to find some slow ones for my next test!
But with a current limited lab supply everything went fine. The outputs got a little warm as the idle current climbed up to 40ma , but a touch with the fingertip on the vbe transistor made it come back down to 25ma. That indicates thea the bias servo works as intended.
Fuses are fast blow, need to find some slow ones for my next test!
Testing the power supply
Here is power supply being load tested using four 15ohm/20W resistors in a series/parallel configuration, which simulates the load from the two amp modules under full load.
The voltage under load drops from 41.5V unloaded to around 34V while the load current is 2.3A, which means that around 80W need to be dissipated by the resistors.
After one hour the whole thing got very hot, but nothing blew up! I ran the test for around two hours and by then even the 100VA rated transformer got hot. The bridge is rated 25A, but runs so hot that it may need a heatsink.
Later I ran another but shorter test where the voltage dropped to 33V and the current was 2.67A. Still nothing blew and no smoke was detected!
I still have trouble with the 4A fuses on the PSU board. They blow at startup because of the inrush current into the 20mF capacitance. So far I had no luck locating any slow blow fuses, but then I installed a 22ohm thermistor (the little black part on the smaller board to the left) on the mains fuse board. It helps some, but the price is one volt lost across the thermistor and some additional heat being dissipated.
Work continues, next step will be start of the installation in the case.......
Here is power supply being load tested using four 15ohm/20W resistors in a series/parallel configuration, which simulates the load from the two amp modules under full load.
The voltage under load drops from 41.5V unloaded to around 34V while the load current is 2.3A, which means that around 80W need to be dissipated by the resistors.
After one hour the whole thing got very hot, but nothing blew up! I ran the test for around two hours and by then even the 100VA rated transformer got hot. The bridge is rated 25A, but runs so hot that it may need a heatsink.
Later I ran another but shorter test where the voltage dropped to 33V and the current was 2.67A. Still nothing blew and no smoke was detected!
I still have trouble with the 4A fuses on the PSU board. They blow at startup because of the inrush current into the 20mF capacitance. So far I had no luck locating any slow blow fuses, but then I installed a 22ohm thermistor (the little black part on the smaller board to the left) on the mains fuse board. It helps some, but the price is one volt lost across the thermistor and some additional heat being dissipated.
Work continues, next step will be start of the installation in the case.......
Attachments
A 100VA, 25Vac plus 25Vac transformer has an AC continuous current rating into your resistive load of 2Aac.
The continuous DC current after a capacitor input filter is ~1Adc.
The recommended continuous DC current is much less than 1Adc. I adopt <=~50% of the DC rating to keep the transformer cool enough for long term operation (20years to 40years).
The inside of your transformer would have been very much hotter than the surface temperature.
Your experiment may have permanently damaged the insulation inside the transformer !!!!!!
The continuous DC current after a capacitor input filter is ~1Adc.
The recommended continuous DC current is much less than 1Adc. I adopt <=~50% of the DC rating to keep the transformer cool enough for long term operation (20years to 40years).
The inside of your transformer would have been very much hotter than the surface temperature.
Your experiment may have permanently damaged the insulation inside the transformer !!!!!!
Hi AndrewT , and thank you for the warning! But I can see no problem since the voltage is only 30 volts ac and not 50! At 100VA it means that the transformer can deliver 100V/30A=3.33A ac.
I tested at approximately 80-85% of the transformer rating for around two hours and there was no funny smell or smoke detected. And I believe that it will never be loaded like that again during its lifetime.
But should it melt down, my local friendly transformer winder will happily make me another one....
I tested at approximately 80-85% of the transformer rating for around two hours and there was no funny smell or smoke detected. And I believe that it will never be loaded like that again during its lifetime.
But should it melt down, my local friendly transformer winder will happily make me another one....
it is the heating that limits transformer capacity, how hot was your traffo when you did your test?
voltage regulation, the level of rail sag you are happy to live with will determine if you want a bigger traffo...
listening to music and sine wave testing are two different things, but if your traffo and amp set-up can survive sine wave testing, then it will survive everyday listening to music..guaranteed...
voltage regulation, the level of rail sag you are happy to live with will determine if you want a bigger traffo...
listening to music and sine wave testing are two different things, but if your traffo and amp set-up can survive sine wave testing, then it will survive everyday listening to music..guaranteed...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.